The MiniMIPS assembler

1. Downloading the MiniMIPS assembler

SPIM, which gets its name from reversing "MIPS", is a simulator for the MiniMIPS assembly language.

The website which contains the simulator is here. You can follow it to download the version you feel the most convenient to use.

You can log into one of Linux machines in our lab and execute the following command to start a graphical interface for using the simulator.

$qtspim

However, the version for Windows is more convenient. If you have a Windows machine in your home, it is strongly suggested that you use Windows' version. All the versions are equivalent in terms of the functions they provide and have the same user interface.

2. The user interface

After you launched the simulator, you will see its main window popping up.

The first step is to go to the Help menu, which shows you a tutorial as how to use the simulator. It is a simple tutorial, which contains all you need to use the simulator. A couple of notes are in order.

• How to load and run an assembly program is detailed in the tutorial.
• The left panel contains two tabs. Always focus on the Int Regs tab. The other tab is for float-point number registers, which is not covered in the course.
• The right panel contains two tabs, Data and Text. You will switch back and forth between them during your assembly programming/debugging.
• You can clear the contents of registers by accessing the top menu item Simulator.

3. A sample program

You must first use your preferred text editor to input your assembly program.

A good sample assembly program is posted here. Please try it by changing some parts of it and see what happens.

Please pay attention to the following places.

• The directive .globl main tells the main entrance to your program. However, the simulator starts executing earlier than this point. Press Single Step (F10) to go through until you are at the main entrance to your program. From there it's your program.
• Some pseudoinstructions are converted into more than one basic instruction.
• Check the contents of registers frequently.
• Check the content of memory frequently.
• You will find F10 is very useful.

You need to practice with the simulator. The more you practice, the more you will feel comfortable with it.

We have studied the instruction set of the MiniMIPS assembly language in class. Please read below some other usefule documents related to the language.

Pseudoinstructions in the MiniMIPS assembly language
Assembler directives in the MiniMIPS assembly language
Input and output in the MiniMIPS assembly language
Macroinstructions in the MiniMIPS assembly language